A communication system can be seen as a facility that enables communications between two or more nodes such as fixed or mobile communication devices, access points such as base stations, servers and so on. A communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols can define the manner how communication devices shall communicate with the access points, how various aspects of the communications shall be implemented and how the equipment shall be configured.
Signals can be carried on wired or wireless carriers. Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). Wireless systems can be divided into coverage areas referred to as cells, and hence the wireless systems are often referred to as cellular systems. A cell can be provided by a base station, there being various different types of base stations and cells.
A user can access the communication system by means of an appropriate communication device or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling receiving and transmission of communications such as speech and data. The communication device may access a carrier provided by a base station, and transmit and/or receive communications on the carrier.
An example of cellular communication systems is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP). A recent development in this field is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. In LTE base stations are commonly referred to as enhanced NodeBs (eNodeB; eNB). An eNodeB can provide coverage for an entire cell or similar radio service area.
Importance and potential of cellular communication systems for public safety has been recognised. For example, the possibility of being able to communicate video data is considered as a critical aspect of various public-safety applications. Video data can be used, for example for surveillance applications, for improving situation awareness during critical missions and/or for improving co-operation between different groups and teams involved e.g. in response to a natural disaster or accident or other unexpected incident. Wireless video application support for different incidents has however been unavailable or limited due to limited capacity, in particular uplink (UL) capacity. This can be especially the case in locations where large cell area coverage is provided. Multiple high definition (HD) cameras can demand dense cell deployment, multiplying the number of cell sites required for achieving wide geographical coverage. Still, even with dense cell deployment, the video coverage cannot necessarily be guaranteed. For example, this may be limited by interference from other cells and/or depend on the load in interfering (e.g. neighbouring) cells.
Certain systems such as the LTE can deploy a frequency reuse scheme. This means that low signal-to-interference ratios (SIR) may occur when the same time-frequency resource is used in neighbouring cells. SIR as low as −5 dB or even lower may exist in a cell border. This can result spectrum efficiency as low as 0.1 bit/Hz. Considering 512 kbps as the minimum bit rate requirement for a video application, the required bandwidth for one good enough video application may be 5 MHz. Thus, if e.g. a major accident happens in a cell border area, the video capacity can be very poor.
Reliability of data transmission can be increased by selecting a sufficient low data rate in the combination with hybrid automatic repeat request (H-ARQ) mechanism. This is not especially efficient, and a cell may not be able to offer sufficient capacity for multiple video applications.
Radio resource release methods have also been considered in the context of flexible spectrum use between different radio access technologies or between different operators. In these scenarios, different systems can have primary and secondary access rights on the spectrum. The system, or cell, with secondary access rights can be required to release the requested radio resources. These solutions are not considered suitable for use in mission critical communications and public safety applications as it is not possible to assign appropriate access right classes to different cells beforehand, for example before an accident takes place. Also, multiple cells may simultaneously be needed to support mission critical communications. A mandatory resource release cannot be required from a cell supporting mission critical communications. In other words, the different access rights cannot be used to ensure sufficient capacity in an area of emergency as the precise location and/or cell where the need for communication of critical data arises cannot typically be predicted. After an incident, for example a major accident, the response should nevertheless be quick. This may require that the required capacity for video and other critical data should be available as soon as possible without a need for any specific configurations to be made after the incident. If possible, disruption to other communications should be kept minimal.
It is noted that the above discussed issues are not limited to any particular communication environment and station apparatus but may occur in any appropriate system enabling multiple uplink connections.